1. Field of the Invention
The invention relates to a magnetic tape cassette which is adapted to cooperate, in a first position and in a reversed second position, with parts of a cassette recording and/or playback apparatus (hereinafter referred to as a cassette apparatus); and more particularly to a cassette having first and second adjacently disposed reel hubs, which are rotatable about parallel spaced first and second axes of rotation in a cassette housing; a length of magnetic tape having a first end connected to the first reel hub and having a second end connected to the second reel hub, so as to enable it to be wound from the first reel hub to a reel on the second reel hub and back from the second reel hub to a reel on a first reel hub, and having a stretched tape portion along a front opening of the cassette housing for cooperation with parts of a cassette apparatus; and cover means connected to the cassette housing and pivotable relative thereto about a pivoting axis which is parallel to the main walls between a closed position and an open position. In the closed position, the cover extends along the front of the cassette housing, to at least partly cover the stretched portion of the magnetic tape and thus protect the magnetic tape against inadvertent damaging when the magnetic tape cassette is not placed on a cassette apparatus. The open position, when the magnetic tape cassette is placed on a cassette apparatus, allows parts of the cassette apparatus to cooperate with the stretched portion of the magnetic tape.
Magnetic tape cassettes in a variety of versions have gained a high degree of popularity in various fields of application. This may be attributed to the high vulnerability of the magnetic tape medium when not accommodated in a cassette. The magnetic tapes commonly used in magnetic tape equipment for the consumer market and also for many semiprofessional and professional uses have a thickness dimension which is very small in comparison with the width dimension. The thickness dimensions generally range between 15 and 40 um, while the width for the more customary magnetic tapes varies roughly between 12 and 25 mm. The magnetic tapes consist of a plastic foil which on one side is provided with a finely dispersed magnetizable material, and has an extremely high degree of flexibility. The magnetic tape cassette affords protection against damaging of the delicate and vulnerable magnetic tape, so that the ease of handling the magnetic tape medium is substantially improved.
For many simple applications it suffices if the front of the cassette is at least partly closed and is provided with openings for the passage into the cassette of parts of a cassette apparatus, such as a recording/playback head, an erase head and a pressure roller. Such a cassette is for example the so-called Compact Cassette, also referred to as the Philips cassette, which is generally used for audio purposes. With this cassette the magnetic tape need never be removed from the housing, so that the front may be partly closed and thus affords adequate protection of the magnetic tape against inadvertent touching. While dust can reach the magnetic tape through the openings, this seldom presents a problem in that tape application.
Still other known cassettes are intended for use with a cassette apparatus which includes a device for partly withdrawing the magnetic tape from the cassette housing and bringing the portion of the magnetic tape thus removed from the cassette housing into contact with the magnetic heads. For audio applications this enables a better guidance of the magnetic tape during its transport from the one reel to the other along the magnetic heads to be obtained, so that higher quality standards in respect of signal recording and reproduction can be achieved than with the previously mentioned Compact Cassette, in which the lace-up is determined by components of the cassette housing.
In known magnetic video tape equipment for home-entertainment use, which to date are always equipped with rotary magnetic heads which write obliquely oriented closely spaced tracks on the magnetic tape, the magnetic tape should also be withdrawn from the cassette housing. The front of the cassette housing must then be free of wall portions which could interfere with the withdrawal of the magnetic tape from the cassette housing. As a result of the absence of wall portions at the front the likelihood of the magnetic tape being touched inadvertently increases. This likelihood is further increased because the cassette apparatus customarily includes a device for withdrawing the magnetic tape from the cassette housing. Such a device enters the cassette housing through the main walls behind the magnetic tape and should engage the back side of the magnetic tape during withdrawal. Therefore, cut-outs which extend to the front are necessary in the main walls of the cassette. These cut-outs expose the edges of the magnetic tape, which exposure greatly increases the likelihood of the magnetic tape being damaged.
Another aspect of cassette design is that, when magnetic tape cassettes are used on equipment which enables higher quality audio recording and reproduction or which enables video signals to be recorded and reproduced, dust should be prevented from reaching the magnetic tape as far as possible, because dust may affect the high quality of recording and reproduction.
Therefore many magnetic tape cassettes are provided with movable cover means in order to protect the stretched portion of the magnetic tape which extends along the front of the magnetic tape cassette when the magnetic tape cassette is not located on a cassette apparatus.
2. Description of the Prior Art
Magnetic tape cassettes which are suitable for use on a cassette apparatus in a first position only and which are consequently not suitable for cooperating with the apparatus in a reversed or "flipped over" second position, so-called non-reversible cassettes, present fewer problems in respect of the protection of the magnetic tape, because only one of the two main walls need be provided with cut-outs for withdrawal of the magnetic tape from the cassette. Such a cassette is for example known from U.S. Pat. No. 3,900,172. A cassette cover closes the front of the cassette housing if the cassette is removed from a cassette apparatus. On its side which faces the rear of the cassette the cassette cover has an additional ridge which covers the back side of the magnetic tape when the cassette cover is closed. Although one of the main walls of the cassette has a comparatively large opening this still provides satisfactory protection of the magnetic tape. However, dust can still rather easily reach the magnetic tape, and the tape can readily be damaged by the ridge if the stretched portion of the magnetic tape in the cassette is not sufficiently taut.
In the case of reversible magnetic tape cassettes this solution cannot be adopted. If the housing of a reversible magnetic tape cassette has cut-outs in the main walls for withdrawal of the magnetic tape from the magnetic-tape cassette, the cut-outs should be formed in both main walls. From German Offenlegungsschrift No. 2,552,063, to which U.S. Pat. No. 4,021,006 corresponds, a reversible magnetic tape cassette of this type is known, having two cassette covers which partly extend along the front of the cassette housing: a first cassette cover on the side near the first main wall of the cassette housing, and a second cassette cover on the side near the second main wall of the cassette housing. When the cassette covers are closed a part of the first cassette cover is situated in the plane of the first main wall and a part of the second cassette cover is situated in the plane of the second main wall. At the front of the magnetic tape cassette perpendicular to these parts, half-height front cover portions extend parallel to the rear of the cassette housing, and are thus perpendicular to the first-mentioned parts of the cassette covers. The first cassette cover is pivotable about a first pivoting axis disposed near the first main wall of the cassette housing and the second cassette cover is pivotable about a second pivoting axis disposed near the second main wall of the cassette housing. The two pivoting axes are parallel to each other and parallel to the main walls. The two cassette covers also have gear-segments which engage with each other. When the one cassette cover is pivoted the second cassette cover is thus pivoted simultaneously and to the same extent. Each cassette cover covers the front of the cassette housing over half its height.
When this known magnetic-tape cassette is placed on a cassette apparatus, a unit on the deck of the cassette apparatus partly opens the two cassette covers, after which the magnetic heads are brought into contact with the magnetic tape through the slot between the two cassette covers. The magnetic tape cassette has cut-outs in the main walls for bringing the magnetic tape into contact with two pressure rollers by means of two capstans on either side of the magnetic head, which capstans are situated behind the magnetic tape.
A disadvantage of this known cassette is that both in the first and in the second position of the magnetic tape cassette on a cassette apparatus the two cassette covers must be opened. One of the two cassette covers is then always pivoted into a position in which it moves toward and faces the cassette apparatus. In the cassette apparatus the magnetic tape cassette should therefore be supported in such a way that there is sufficient clearance between the main wall of the magnetic tape cassette which faces the cassette apparatus and the parts of the apparatus near that wall. Another drawback is that the opened cassette covers constitute an obstruction to the device which withdraws the magnetic tape from the cassette, unless the cassette covers are opened very far. This last alternative demands a still greater clearance. Otherwise both sides adjacent the cassette covers must have cut-outs formed which open towards the front, as in the known cassette, so that the magnetic tape is exposed at these locations. The spaced required above the cassette for the opened cassette cover is comparatively large, because the cassette cover portion which is disposed in the main wall also pivots upwards. This is a drawback because the overall height of a cassette apparatus should be minimized for obvious reasons.
Therefore, the known magnetic tape cassette is less suitable for application where the magnetic tape is to be withdrawn from the cassette housing. Moreover, unless openings are formed in the main walls of the cassette housing on both sides of the cassette covers for the passage of the tape withdrawal elements of a cassette apparatus, which means that there will be locations on both sides of the cassette covers where the magnetic tape can be touched and damaged, the two cassette covers should be pivoted into their open positions before the magnetic tape cassette is moved to an operating position over the withdrawal elements of the cassette apparatus. However, for thus swinging open the cassette covers before the magnetic tape consists is completely in its operating position, the known magnetic tape cassette is less suitable because of the actuation elements for the cassette covers which are then required. Further, the part of the cassette cover which faces the deck of the cassette apparatus and which is situated at the front of the cassette housing constitutes an obstruction for the withdrawal elements even if the cassette covers are swung open very far.